High Definition Multimedia Interfaces (HDMIs (registered trademark)) have been becoming popular as communication interfaces for high-speed transmission of uncompressed (baseband) image signals (image data) and digital audio signals (audio data) accompanying the image signals. The data transmission end connected via an HDMI interface is an HDMI source device, and the data reception end is an HDMI sink device.
In an example of an AV system or the like, a Blu-ray Disc (BD) recorder, a set top box (STB), and some other audio visual source (AV source) as HDMI source devices may be connected to a television receiver, a projector, and some other display as HDMI sink devices by HDMI interfaces (see Patent Document 1, for example). Further, a control method is defined for content to be provided by an HDMI source device such as a BD recorder, on the assumption that the BD recorder is controlled and selected directly from an HDMI sink device such as a television receiver, and a screen is displayed on the HDMI sink device.
Meanwhile, inter-device control according to digital living network alliance (DLNA) has also been put into practical use as a control scheme with the IP (Internet Protocol). DLNA defines 2-Box Pull System Usage formed with a digital media server (DMS) as a content providing server and a digital media player (DMP) as a client that reproduces data, and 3-Box System Usage having a digital media renderer (DMR) and a digital media controller (DMC) as clients. In the latter 3-Box System, the DMC is operated so that content can be transmitted from the DMS to the DMR and be reproduced. Further, in universal plug and play (UPnP) on which DLNA is based, a content directory service (CDS) function is designed to hierarchize and deliver a list of and information about the content held by a digital media server (DMS), and this can also be applied to DLNA (see Patent Document 2, for example).
In a device configuration in which a DLNA device and an HDMI device coexist, however, HDMI content cannot be controlled from the DLNAdevice. This is because the specifications of content data control with a digital interface such as an HDMI are valid only between devices connected by an HDMI. Besides, DLNA has also suggested a specification of content data control between IP-connected devices, but such a specification does not support control between devices outside its network.
Particularly, there have been user demands for use cases of 3Box Control with a mobile terminal device serving as a device that controls devices, like a mobile digital media controller (M-DMC) of DLNA. However, HDMI content cannot be controlled in such cases.